StartTLS URL extension

[Howard Chu <hyc@symas.com>]

We really ought to have a way to allow clients to make libldap use StartTLS 
without having to code their own calls into libldap for that purpose. I think 
it would be useful to allow specifying StartTLS in the extension field of the 
LDAP URL. Then at least it can be configured into ldap.conf forgotten about.

The code for ldap_initialize() should look for the URL extension field, and 
act on it if StartTLS / 1.3.6.1.4.1.1466.20037 is present.

Any comments?
--
  -- Howard Chu
  CTO, Symas Corp.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/